Clarify Callable requirement

Author: ab5tract

doc/Type/Callable.pod6

@@ -41,6 +41,17 @@ container, is has to implement Callable.
     my &a = A;
     say a(); # OUTPUT: «called␤»
 
+Applying the Callable role is not a requirement, however, should a class simply want to add subroutine-like semantics in a regular scalar container.
+
+	class A {
+		has @.values;
+		submethod CALL-ME(Int $x where 0 <= * < @!values.elems) {
+			@!values[$x]
+		}
+	}
+	my $a = A.new: values => [4,5,6,7]
+	say $a(2); # OUTPUT: «6␤»
+
 =head2 method Capture
 
 Defined as:
@@ -51,4 +62,4 @@ Throws C<X::Cannot::Capture>.
 
 =end pod
 
-# vim: expandtab softtabstop=4 shiftwidth=4 ft=perl6
+# vim: expandtab softtabstop=4 shiftwidth=4 ft=perl6